Using LIDAR DEMs with ArcView Spatial and 3D Analysts

1
Using LIDAR DEMs with ArcView Spatial and 3D
Analysts
Dean Whitman, Ph.D. International Hurricane
Center Florida International University
FIU GIS-RS Center November, 15, 2002
2
Workshop Outline

• Project Overview
• Data Collection and Processing
• Description of Datasets
• Internet Access to Data
• Exercises
• Data Import and Visualization
• Information extraction
• 3D Visualization (Time Permitting)
• QA

3
FEMA Windstorm Simulation and Modeling Program

• Scope
• LIDAR data acquisition
• Storm Surge Model Comparison
• Computer Animation
• Public awareness/education
• Participating Counties
• Broward
• Palm Beach
• Miami-Dade
• Manatee

4
FIU/UF LIDAR System

• Optech 1210 ALTM system
• Delivered March 1999
• Mounted in Cessna 337 twin-engine aircraft
• System and aircraft jointly owned by FIU/IHC and
  UF Geomatics program
• Upgraded to model 1233 in 2002

5
OPTECH 1233 Features

• 330 - 2000 m operating altitude
• 33 kHz laser repetition rate
• to /- 20 degrees scan angle , 30 Hz scan rate
• 10 - 30 cm spot diameter
• 10 - 50 cm RMS vertical accuracy (depending on
  swath width)
• Returns first, last range reflection intensity

6
(No Transcript)
7
Aircraft
8
GPS Ground Station
9
LIDAR Measures Objects From Line of Sight
10
Cloud of Returns
11
LIDAR 1st and Last Stop
1ST stop from canopy
Last stop from ground
12
Terrain Filtering of Irregularly Spaced Points
After
Before
13
Gridded Top Surface and Bare Earth DEMs
14
Data Processing Steps

• Compute Aircraft Trajectory from GPS
• Calculate XYZ of laser points
• Merging and tiling of swaths
• Remove vegetation and other features
• Gridding and interpolation
• Validation and inspection of results

15
Processing Flow
16
Datasets

• Strip Data
• 9 column ASCII text files (T,x1,y1,z1,i1,x2,y2,z2,
  i2)
• 5000x5000 ft Tiles
• Unfiltered 1st return data (Top Surface)
• X,Y,Z points (ASCII text)
• 5 ft DEMs (Binary Grids)
• Filtered Last return data (Bare Earth)
• X,Y,Z points (ASCII text)
• 5 ft DEMs (Binary Grids)
• Subaveraged Bare Earth DEM Mosaic
• Tiles mosaiced and subaveraged to 100 ft postings

17
Tile OrganizationPoints
150 ft. buffer
3 column (x,y,z) ASCII text 940000_695000_150.asc
SW Corner Coordinates x 940000 y 695000
18
Tile OrganizationGrids
Last column, row overlaps with 1st column, row of
adjacent tiles
1st cell
ASCII header file 940000_695_Z.hdr NCOLS
1001 NROWS 1001 XLLCENTER 940000.0 YLLCENTER
695000.0 CELLSIZE 5.0 NODATA_VALUE
1.701410e038 BYTEORDER LSBFIRST
Binary Floating Point file 940000_695000_Z.flt
Center of last (SE) cell x 945000 y 695000
Center of SW grid cell x 940000 y 695000
5000 ft.
19
Internet Access

• Allows selection and download of data in single
  or multiple tiles
• Uses ARC IMS Technology
• Still under construction
• URL
• http//gis.ihc.fiu.edu/website/lidar

20
Exercises
21
Materials on CD

• Sourcedata ?Materials used in exercises
• 5 ft Top surface and Bare earth DEMs
• 1 ft orthophotos (TIF images)
• Scripts, legends, shapefiles used in exercises
• Samples ? other materials
• Compressed (gzip) Strip file, point tiles
• Subaveraged 100 ft grids, Broward, Palm Beach Co.
• Vertcon94e.asc ? VERTCON model for SE U.S. (in
  DD)
• Used to transform between NGVD29 and NAVD88
• Z88 Z29 VERTCON
• Br_pb_tileindex_dd.shp

22
Overview of Exercise 1Data Import and
Visualization

• Load ArcView extensions and set working directory
• Import binary raster DEM files to GRIDs
• Visualization Color shaded relief images
• Create 1 ft. contours
• Overlay 1 ft orthophotographs

23
Overview of Exercise 2Information Extraction

• Point query and extraction
• Gridspot.ave script
• Extracting elevation profiles
• Interpolate Line, Profile Graph tools
• Extracting zonal statistics within polygons
• Summarize Zones tool

24
(No Transcript)